Gasoline stove

ABSTRACT

This invention relates to a stove for burning various hydrocarbon fuels such as gasoline, naphtha, kerosene and the like and more particularly is directed to an improved burner construction for portable stoves of this type which may be used by campers, back-packers, mountain climbers and others interested in the outdoors.

United States Patent [191 Penber thy Aug. 13, 1974 GASOLINE STOVE [76]Inventor: Harvey Larry Penberthy, 5624 SW. Admiral Way, Seattle, Wash.98116 [22] Filed: Apr. 20, 1973 [21] Appl. No.: 352,948

52 U.S. Cl. 431/2 27 [51] Int. Cl. F23d' 11/44 [58] Field of Search431/218, 227, 344; 126/43, 126/44; 239/5903 [56] References Cited UNITEDSTATES PATENTS 2,363,098 11/1944 ,Tullis ..l26/44X 2,465,572 3/ 1949Bramming 126/44 X Primary Examiner-Edward G. Favors Attorney, Agent, orFirm-Le Blane & Shur [5 7] ABSTRACT This invention relates to a stovefor burning various hydrocarbon fuels such as gasoline, naphtha,kerosene and the like and more particularly is directed to an improvedbumer construction for portable stoves of this 7 type which may beusedby campers, back-packers, mountain climbers and others interested in theoutdoors. I

13'Claims, 6 Drawing Figures PAIENIH! nus! 31914 amena- SHEET 2 u! 2FIG. 3

GASOLINE STOVE cooking utensil may be supported directly above theburner to receive heat from it.

One of the difficulties associated with the use of liquid fuels in smallportable stoves is the problem of insuring complete vaporization of theliquid fuel prior to combustion. Attempts to overcome this problem haveresulted in a variety of proposed devices for incorporation in the stoveburner adjacent the burner orifice to enhance vaporization and improvefuel combustion. Incomplete vaporization in addition to reducing theefficiency of fuel consumption tends to produce deposits of lessvolatile hydrocarbon products in the burner and these deposits have atendency to clog the burner orifice after the stove has been used foronly a relatively short period of time. However, insofar as applicant isaware, none of these attempts have been completely successful and it isconventional in portable cooking stoves to incorporate a cleaning rodhaving a needlelike point or tip which may be inserted into the burnerorifice to unclog the orifice and remove hydrocarbon materials that havebeen deposited in it. In addition to increasing the cost of the stovethe use of cleaning rods is at the very least an annoyance to the campersince they do not prevent clogging and only serve to remove depositsafter the burner has become partially or wholly ineffective. Further,deposits dislodge by the cleaning rod may come to rest in the fuel lineonly to be carried by gasoline and/or vapor back to the orifice wherethey again clog the orifice and have to be removed.

For example, in one known type of stove construction the stoves areprovided by the manufacturer with a jet (sometimes called tip) cleaningtool. This tool consists of a very fine wire, commonly.0.0l inch indiameter, mounted on a small handle. The user isinstructed to clean theopening in the jet by inserting the fine wire of the tool several timeswhile the stove is operating. In some stoves, this tip-cleaning wire orneedle is built into the vaporizer section and is caused to enter theorifice in the jet by working a small rotating handle.

The present invention relates to an improved construction for burningliquid fuel in portable stoves of the type used by hunters, campers,back-packers and the like. In particular, the invention is concernedwith improving the reliability of the stove burner with the avoidance ofmalfunction due to clogging of the fuel jet of the burner.

The novel construction of the stove burner jet of the present inventioneliminates the clogging described above and, therefore, eliminates theneed for any orifice cleaning needle.

In the present invention, substantially complete vaporization of thefuel is achieved by requiring the fuel to travel a long helical pathwhere the fuel is subjected to the heating action of a substantial massof metal. In addition, the present invention provides a pre-crackingdevice in the form of a metal screen within the jet itself.

This screen is press-fit into the jet and is substantially at the sametemperature as the jet. The holes in the screen are smaller than thediameter of the jet orifices so that any particles which can passthrough the screen also pass through the orifice. More importantly, thefact that the screen is at the same temperature as the jet means thatthere is no further cracking of the longer-chain hydrocarbons in thespace between the screen and orifice and thus there is no deposition ofcarbon in the orifice. The screen traps any particles which may 7 comethrough from dirty fuel and these particles are such that they do notclog the screen. The ends of the wires comprising the screen aresubstantially all in pressed contact with the jet and are atsubstantially the same temperature as the jet. Due to the good heatconductivity of the metal screen, the heat from the jet is transportedthrough and about the screen wires so that substantially the sametemperature exists across the entire screen.

It is therefore one object of the present invention to provide animproved stove for burning liquid fuels.

Another object of the present invention is to provide an improved liquidfuel burning stove of the small portable type particularly adapted foruse by campers, hikers and the like.

Another object of the present invention is to provide an improved burnerconstruction for portable liquid fuel burning stoves.

Another object of the present invention is to provide a stove burnerhaving improved fuel vaporization characteristics suitable for burning avariety of hydrocarbon fuels such as gasoline, naphtha, kerosene and thelike.

Another object of the present invention is to provide an improved stoveburner in which a transversely extending hydrocarbon pre-cracking screenis provided directly in the burner jet adjacent the jet orifice.

Another object of the present invention is to provide an improved stoveburner construction in which a liquid fuel is first substantiallyvaporized by passing it through a helical path adjacent a relativelylarge mass of hot metal and then passed through a pre-cracking screen atsubstantially the temperature of the burner jet orifice.

Another object of the present invention is to provide an improved burnerconstruction for liquid fuel stoves which eliminates the deposition ofuncracked and partially cracked material in the burner jet orifice andtherefore eliminates the need for frequent cleaning of the jet orificeby a cleaning rod or cleaning needle as in previous constructions.

Another object of the present invention is to provide a portable campstove with an improved burner construction which is less susceptible toorifice clogging.

These and further objects and advantages of the invention will be moreapparent upon reference to the following specification, claims andappended drawings wherein:

FIG. 1 is a top plan view of a portion of a portable cooking stoveconstructed in accordance with the present invention;

FIG. 2 is an elevational view with parts in section of the stoveillustrated in FIG. 1;

FIG. 3 is an enlarged vertical cross section through the burner portionof the stove illustrated in FIG. 2;.

FIG. 6 is a plan view of the burner jet filter screen prior to insertioninto the burner jet.

Referring to the drawing, and particularly to FIGS. 1 and 2, the novelstove of the present invention is generally indicated at 10 and is ofthe portable type generally used by back-packers. Liquid fuel such asgasoline is contained in a fuel tank 12 and is pressurized by an airpump or the like so that when valve 14 is open the liquid fuel passesunder pressure into a fuel tube 16. The fuel tube passes through thevertical wall 18 of a metal cup 20. Enclosed within tube 16 is a wicking22 preferably made of fine wires or fiberglass. From fuel tube 16 thefuel passes into a burner assembly generally indicated at 24.

Burner assemly 24 includes a burner cup 26 of generally outwardly andupwardly flaring conical configuration provided with suitable aperturessuch as the aperture 28 illustrated in FIG. 2 permitting entry of airinto the interior of the burner cup. The apertures 28 by way of exampleonly may be four or six in number to permit the entry of combustion air.Overlying the upper end of burner cup 26 is a flame spreader 30including a central solid circular disc 32 with four integral andoutwardly extending arms 34. These arms are each crimped over at theirends as indicated at36 to overlie and tightly engage the upper annularedge of burner cup 26 so as to support the flame spreader at the upperend of the cup.

The metal cup or body 18 is provided at its upper end with an outwardlyextending annular flange 38 and attached to this flange or rim are theopposite ends of a pair of support wires 40 and 42 which run parallelacross the stove body to provide a support for a cooking pan or othercooking utensil which may be placed on the support wires 40 and 42. Theburner assembly 24 is supported within the cup or body 18 by means of ascrew 44 passing through a suitable aperture in the center of the bottomwall 46 of the cup and threaded into a primer cup 48 forming a part ofthe burner assembly.

FIG. 3 shows the burner assembly 24 to an enlarged scale and like partsbear like reference numerals in that figure. Primer cup 48 is providedwith internal threads 50 adapted to engage the threads on the screw 44of FIG. 2 and an annular well 52 formed by the body of the primer cupand the outer annular flange 54. Primer cup 48 is in turn secured to avaporizer in the form of an elbow 56 having a central passageway 58receiving one end 60 of the fuel tube 16. The end 60 of the fuel tube ispreferably secured to the elbow 56 as indicated at 62. Received withinthe passageway 58 is a solid metal plug 64 having helical threadsdefining grooves 66 which form with the adjacent vertical wall 68 of theelbow an annular helical passageway for the fuel.

The upper end 70 of elbow 56 is externally threaded to receive theinternally threaded collar 72 of the burner cup 26. Upper end 70 of theelbow 56 is also internally threaded to receive a burner jet 74 providedwith a burner orifice 76. Positioned within jet 74 closely adjacent tothe orifice 76 is a fine wire mesh 78 having a plurality of openingsthrough which the fuel may pass substantially smaller than the diameterof the jet orifice 76.

FIGS. 4 and 5 show the details of the burner jet 74 and FIG. 6 is a planview of the wire screen 78 prior to its insertion into the jet. Aspreviously described, jet 74 is externally threaded as at 80 forinsertion into the upper end of elbow 56 of FIG. 3 and one end of thejet 78 is provided with a groove or notch 82 adapted to receive the endof a screwdriver for inserting and rotating the jet 74 into the upperend of the elbow. This notch 82 communicates with the orifice 76 formedin a central wall 84 of the jet. The other end of the jet is providedwith a chamber 86 in fluid communication with the other end of jetorifice 76 and which chamber receives the wire screen 78. Wire screen 78is originally preferably of flat circular shape as illustrated in FIG. 6and is inserted into the chamber 86 with its outer edges in tight heatcontacting engagement with the annular wall of chamber 86 so that thewire mesh assumes the generally bowed configuration illustrated. Wiremesh 78 is inserted into the chamber 86 a substantial distance so thatthe central bowed portion of the mesh is close to the orifice 76.

In operation, gasoline is admitted into the fuel tube 16 through thevalve 14 from pressurized tank 12. Liquid gasoline enters elbow 56 andis vaporized. To insure that little or no liquid gasoline passes throughthe elbow to the jet, the fuel is made to flow through the helicalpassageway formed by metal plug 64 and the adjacent vertical walls ofthe elbow. Plug 64 may comprise a screwthreaded metal rod with a lightpress-fit in the passageway of the elbow. The vapor then passes throughthe wire mesh 78 and through orifice 76. The vapor exits from orifice 76with sufficient energy to inspirate air through the slots 28. Thecombined fuel vapor and air strike spreader 30 which deflects the gasesoutwardly in all directions toward burner cup 26 where active combustiontakes place. The flame is deflected upwardly from the burner cup 26toward the bottom of the cooking utensil resting on the support wires 40and 42. In starting the stove the elbow 56 is customarily preheated toabove the boiling point of gasoline. This is done by adding liquidgasoline or alcohol to the reservoir 52 of the priming cup 48 andsetting it afire.

Liquid fuel such as gasoline, naphtha and kerosene, are commonlymixtures of various low boiling point fractions of petroleum. Whenstored for an extended period of time such as a few months to a fewyears, some of these hydrocarbon fractions recombine to form varnishesand gum. These degradation products of the original liquid do notvaporize uniformly and instead tend to crack or decompose when heatedwith the formation of free carbon which deposits on the hot metalsurfaces. The accumulation is not stable, however, and comes looseoccasionally in small chunks which are large enough to clog a fuelorifice.

Further, there is some possibility at higher burning rates that dropletsof fuel can go through a conventional vaporizer carried along by theportion of the fuel which has vaporized so that droplets of liquid fuelcan get to the orifice itself. There vaporization takes place with thedeposition of these higher molecular weight hydrocarbons such asvarnishes. A coating then builds up on the jet which must be removedfrom time to time.

' For this reason, previous portable stoves have usually metal of elbow56 and the other side by the metal of plug 64. The metal and plug areheated by the conduction of heat from the burner cup 26. I have notfound it necessary to have the vaporizing helix plug 64 in leak-tightrelationship at the peak of its threads with elbow 56. It is sufficientthat the clearance between the peak of the threads and the bore in theelbow is small enough to prevent significant droplets of gasoline fromgoing through without being vaporized.

A more important aspect of the present invention which avoids theclogging of prior art stoves is the provision of the metal screen ormesh 78 within the jet orifice itself. This screen is press-fit into thechamber 86 in the jet itself and hence is substantially at the sametemperature as the jet. The holes in the screen by way of example onlymay be 0.005 inches in diameter as compared with the diameter of theorifice 76 which in this example may be from 0.010 to 0.030 inch. Thus,any particles which can pass through the screen also can pass throughthe orifice. The screen being of good heat conducting metal itself,being located closely adjacent the jet orifice and in good heatconducting contact with the metal of the jet 74, insures that the wiremesh 78 will be over its entire area at effectively the same temperatureas the jet 74, i.e., between about from 400 to 500 P, so that there isno substantial further cracking of the longer chainhydrocarbons in thespace between the screen 78 and the orifice 76. Thus, there is little orno deposition of carbon in the orifice 76. A further benefit of thescreen 78 is that it traps any foreign particles which have come throughfrom dirty fuel.

These particles are deposited on the screen which screen is ofsufficiently large size that they do not serve to clog the screen.Should the screen become clogged after long periods of usage, it is asimple matter to disassemble the unit, remove it from the jet andreplace it with a new wire mesh screen 78.

In the preferred embodiment the metal elbow, burner cup, flame spreaderand jet are all made of brass for good thermal conductivity. Plug 66 ismade of steel or brass and screen 78 is made of stainless steel orbrass. While a metal screen whose outer peripheral edge is in tight heatconductive contact with the jet is preferred, in some instances screen78 can be replaced with a circular plug of porous heat conducting metalmade by sintering partially-compacted metal powder. The primer cup, ifdesired, can be replaced by a primer pad or primer wick.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States lettersPatent is:

l. A burner assembly for liquid fuel stoves comprising a fuel vaporizer,a fuel jet having a jet orifice with one end of said orifice in fluidcommunication with said vaporizer, a burner cup in fluid communicationwith the other end of said jet orifice, and a pre-cracking heatconductive member adjacent said orifice with openings smaller than thediameter of said orifice, said member extending laterally between saidvaporizer and said orifice whereby all the fuel passing from saidvaporizer to said orifice must pass through said openings, said heatconductive member having an annular portion in tight heat conductivecontact with said jet whereby substantially the entirety of said memberis at effectively the same temperature as said orifice due to proximityto said orifice and heat conduction from said jet.

2. A burner assembly according to claim 1 wherein said pre-crackingmember comprises a resilient wire mesh having its outer edgesresiliently urged in press fit engagement with said jet.

3. A burner assembly according to claim 2 wherein said wire meshcomprises a plurality of criss-crossing wires, said wires each havingits ends contacting said jet whereby heat from said jet is conductedthrough each of said wires from each of its ends.

4. A burner assembly according to claim 1 wherein the openings in saidpre-cracking member are approximately 0.005 inch wide.

5. A burner assembly according to claim 4 wherein the diameter of saidorifice is from 0.010 to 0.030 inch.

6. A burner assembly according to claim 1 wherein said vaporizercomprises a tubular metallic elbow, and a primer cup adjacent said elbowfor applying primer heat to said vaporizer.

7. A portable liquid fuel stove comprising, a fuel tube for receivingliquid fuel under pressure, a vaporizer coupled to said liquid fueltube, a fuel jet having a jet orifice coupled to said vaporizer, aburner cup having apertures for inspirating air into said cup, theinterior of said burner cup being in fluid communication with the outletend of said jet orifice, a flame spreader mounted over the upper end ofsaid burner cup, and a pre-cracking heat conductive member between saidvaporizer and said orifice, said heat conductive member having openingssmaller than the diameter of said orifice and extending laterally of thefuel flow path between said vaporizer and said orifice whereby all ofthe fuel passing from said vaporizer to said orifice must pass throughsaid openings, said heat conductive member being located adjacent saidorifice with at least its outer periphery in tight heat conductivecontact with said jet whereby substantially all of said pre-crackingmember is at the temperature of said orifice due to proximity to theorifice and heat conduction from said jet.

8. A stove according to claim 7 wherein said fuel jet comprises anelongated tubular member including a transverse wall containing said jetorifice and a chamber adjacent said orifice, said heat conductive memberextending laterally across said chamber with its peripheral edge pressfit against the interior wall of said chamber.

9. A stove according to claim 8 wherein said vaporizer comprises anelbow, primer means attached to one arm of said elbow, and said fuel jetbeing removably joined to the other arm of said elbow.

10. A stove according to claim 9 wherein said heat conductive member isat a temperature of from about 400 to 500 F during operation of saidstove.

11. A burner assembly for liquid fuel stoves comprising a fuelvaporizer, a fuel jet having a jet orifice with one end of said orificein fluid communicationwith said vaporizer a burner cup in fluidcommunication with the other end of said jet orifice, and a pre-crackingheat conductive member adjacent said orifice with openings smaller thanthe diameter of said orifice, said member extending laterally betweensaid vaporizer and said orifice whereby all the fuel passing from saidvaporizer to said orifice must pass through said opening, said heatconductive member having an annular portion in tight heat conductivecontact with said jet whereby substantially the entirety of said memberis at effectively the same temperature as said orifice due to proximityto said orifice and heat conduction from said jet, said precrackingmember comprising a resilient wire mesh having its outer edgesresiliently urged in press fit engagement with said jet, said wire meshcomprising a plurality of criss-crossing wires, said wires each havingits ends contacting said jet whereby heat from said jet is conductedthrough each of said wires from each of its ends, the resiliency of saidmesh causing it to bow inwardly at its center into close proximity withsaid jet orifice.

12. A burner assembly for liquid fuel stoves comprising a fuelvaporizer, a fuel jet having a jet orifice with one end of said orificein fluid communication with said vaporizer, a burner cup in fluidcommunication with the other end of said jet orifice, and a pre-crackingheat conductive member adjacent said orifice with openings smaller thanthe diameter of said orifice, said member extending laterally betweensaid vaporizer and said orifice whereby all the fuel passing from saidvaporizer to said orifice must pass through said openings, said heatconductive member having an annular portion in tight heat conductivecontact with said jet whereby substantially the entirety of said memberis at effectively the same temperature as said orifice due to proximityto said orifice and heat conduction from said jet, said vaporizercomprising a tubular metallic elbow, a primer cup adjacent said elbowfor applying primer heat to said vaporizer, and a solid metal plug withhelical threads in one end of said elbow defining with said elbow ahelical passageway for the fuel flowing through said vaporizer.

13. A portable liquid fuel stove comprising, a fuel tube for receivingliquid fuel under pressure, a vaporizer coupled to said liquid fueltube, a fuel jet having a jet orifice coupled to said vaporizer, aburner cup having apertures for inspirating air to said cup, theinterior of said burner cup being in fluid communication with the outletend of said jet orifice, a flame spreader mounted over the upper end ofsaid burner cup, and a pre-cracking heat conductive member between saidvaporizer and said orifice, said heat conductive member having openingssmaller than the diameter of said orifice and extending laterally of thefuel flow path between said vaporizer and said orifice whereby all thefuel passing from said vaporizer to said orifice must pass through saidopenings, said heat conductive member being located adjacent saidorifice with at least its outer periphery in tight heat conductivecontact with said jet whereby substantially all of said pre-crackingmember is at the temperature of said orifice due to proximity to theorifice and heat conduction from said jet, said fuel jet comprising anelongated tubular member including a transverse wall containing said jetorifice and a chamber adjacent said orifice, said heat conductive memberextending laterally across said chamber with its peripheral edge pressfit against the interior wall of said chamber, said vaporizer comprisingan elbow, primer means attached to one arm of said elbow, said fuel jetbeing removably joined to the other arm of said elbow, said heatconductive member being at a temperature of from 400 to 500 F. duringoperation of said stove, and an externally threaded solid metal plugreceived in said other arm of said elbow, said plug forming with saidother arm a helical passageway for fuel flowing to said orifice.

1. A burner assembly for liquid fuel stoves comprising a fuel vaporizer,a fuel jet having a jet orifice with one end of said orifice in fluidcommunication with said vaporizer, a burner cup in fluid communicationwith the other end of said jet orifice, and a pre-cracking heatconductive member adjacent said orifice with openings smaller than thediameter of said orifice, said member extending laterally between saidvaporizer and said orifice whereby all the fuel passing from saidvaporizer to said orifice must pass through said openings, said heatconductive member having an annular portion in tight heat conductivecontact with said jet whereby substantially the entirety of said memberis at effectively the same temperature as said orifice due to proximityto said orifice and heat conduction from said jet.
 2. A burner assemblyaccording to claim 1 wherein said pre-cracking member comprises aresilient wire mesh having its outer edges resiliently urged in pressfit engagement with said jet.
 3. A burner assembly according to claim 2wherein said wire mesh comprises a plurality of criss-crossing wires,said wires each having its ends contacting said jet whereby heat fromsaid jet is conducted through each of said wires from each of its ends.4. A burner assembly according to claim 1 wherein the openings in saidpre-cracking member are approximately 0.005 inch wide.
 5. A burnerassembly according to claim 4 wherein the diameter of said orifice isfrom 0.010 to 0.030 inch.
 6. A burner assembly according to claim 1wherein said vaporizer comprises a tubular metallic elbow, and a primercup adjacent said elbow for applying primer heat to said vaporizer.
 7. Aportable liquid fuel stove comprising, a fuel tube for receiving liquidfuel under pressure, a vaporizer coupled to said liquid fuel tube, afuel jet having a jet orifice coupled to said vaporizer, a burner cuphaving apertures for inspirating air into said cup, the interior of saidburner cup being in fluid communication with the outlet end of said jetorifice, a flame spreader mounted over the upper end of said burner cup,and a pre-crackIng heat conductive member between said vaporizer andsaid orifice, said heat conductive member having openings smaller thanthe diameter of said orifice and extending laterally of the fuel flowpath between said vaporizer and said orifice whereby all of the fuelpassing from said vaporizer to said orifice must pass through saidopenings, said heat conductive member being located adjacent saidorifice with at least its outer periphery in tight heat conductivecontact with said jet whereby substantially all of said pre-crackingmember is at the temperature of said orifice due to proximity to theorifice and heat conduction from said jet.
 8. A stove according to claim7 wherein said fuel jet comprises an elongated tubular member includinga transverse wall containing said jet orifice and a chamber adjacentsaid orifice, said heat conductive member extending laterally acrosssaid chamber with its peripheral edge press fit against the interiorwall of said chamber.
 9. A stove according to claim 8 wherein saidvaporizer comprises an elbow, primer means attached to one arm of saidelbow, and said fuel jet being removably joined to the other arm of saidelbow.
 10. A stove according to claim 9 wherein said heat conductivemember is at a temperature of from about 400* to 500* F during operationof said stove.
 11. A burner assembly for liquid fuel stoves comprising afuel vaporizer, a fuel jet having a jet orifice with one end of saidorifice in fluid communication with said vaporizer a burner cup in fluidcommunication with the other end of said jet orifice, and a pre-crackingheat conductive member adjacent said orifice with openings smaller thanthe diameter of said orifice, said member extending laterally betweensaid vaporizer and said orifice whereby all the fuel passing from saidvaporizer to said orifice must pass through said opening, said heatconductive member having an annular portion in tight heat conductivecontact with said jet whereby substantially the entirety of said memberis at effectively the same temperature as said orifice due to proximityto said orifice and heat conduction from said jet, said pre-crackingmember comprising a resilient wire mesh having its outer edgesresiliently urged in press fit engagement with said jet, said wire meshcomprising a plurality of criss-crossing wires, said wires each havingits ends contacting said jet whereby heat from said jet is conductedthrough each of said wires from each of its ends, the resiliency of saidmesh causing it to bow inwardly at its center into close proximity withsaid jet orifice.
 12. A burner assembly for liquid fuel stovescomprising a fuel vaporizer, a fuel jet having a jet orifice with oneend of said orifice in fluid communication with said vaporizer, a burnercup in fluid communication with the other end of said jet orifice, and apre-cracking heat conductive member adjacent said orifice with openingssmaller than the diameter of said orifice, said member extendinglaterally between said vaporizer and said orifice whereby all the fuelpassing from said vaporizer to said orifice must pass through saidopenings, said heat conductive member having an annular portion in tightheat conductive contact with said jet whereby substantially the entiretyof said member is at effectively the same temperature as said orificedue to proximity to said orifice and heat conduction from said jet, saidvaporizer comprising a tubular metallic elbow, a primer cup adjacentsaid elbow for applying primer heat to said vaporizer, and a solid metalplug with helical threads in one end of said elbow defining with saidelbow a helical passageway for the fuel flowing through said vaporizer.13. A portable liquid fuel stove comprising, a fuel tube for receivingliquid fuel under pressure, a vaporizer coupled to said liquid fueltube, a fuel jet having a jet orifice coupled to said vaporizer, aburner cup having apertures for inspirating air to said cup, theinterior of said burner cup beiNg in fluid communication with the outletend of said jet orifice, a flame spreader mounted over the upper end ofsaid burner cup, and a pre-cracking heat conductive member between saidvaporizer and said orifice, said heat conductive member having openingssmaller than the diameter of said orifice and extending laterally of thefuel flow path between said vaporizer and said orifice whereby all thefuel passing from said vaporizer to said orifice must pass through saidopenings, said heat conductive member being located adjacent saidorifice with at least its outer periphery in tight heat conductivecontact with said jet whereby substantially all of said pre-crackingmember is at the temperature of said orifice due to proximity to theorifice and heat conduction from said jet, said fuel jet comprising anelongated tubular member including a transverse wall containing said jetorifice and a chamber adjacent said orifice, said heat conductive memberextending laterally across said chamber with its peripheral edge pressfit against the interior wall of said chamber, said vaporizer comprisingan elbow, primer means attached to one arm of said elbow, said fuel jetbeing removably joined to the other arm of said elbow, said heatconductive member being at a temperature of from 400* to 500* F. duringoperation of said stove, and an externally threaded solid metal plugreceived in said other arm of said elbow, said plug forming with saidother arm a helical passageway for fuel flowing to said orifice.